C-shaped disc prosthesis

ABSTRACT

Exemplary implants and methods are provided for stabilizing adjacent vertebrae. In one embodiment, an implant is provided having a shape that allows the implant to be positioned between adjacent vertebrae using a posterior approach while avoiding contact with the spinal cord. For example, the implant can include an anterior portion that is adapted to be positioned between adjacent vertebrae, and a posterior portion that is adapted to extend around a spinal cord. In certain exemplary embodiments, the implant can also be configured to allow motion between the adjacent vertebrae.

CROSS REFERENCE TO RELATED APPLICATIONS

The present invention claims priority to U.S. Provisional ApplicationSer. No. 60/584,055, filed on Jun. 30, 2004 and entitled “C-Disc,” whichis hereby incorporated by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to spinal implants and methods.

BACKGROUND OF THE INVENTION

Disease, advancing age, and trauma can lead to changes in various bones,discs, joints, and ligaments of the body. Some changes and trauma oftenmanifest themselves in the form of damage or degeneration to a spinaldisc. This condition often results in chronic back pain, which can beanywhere from mild to severe. This pain can sometimes be eliminated byspinal fusion in which two adjacent vertebral bodies are jointedtogether after removing the intervening intervertebral disc. Aprosthetic device is usually placed between the two adjacent vertebralbodies, in place of the removed disc, to fill the space left by theremoved disc and to allow bone to grow between the two vertebral bodies.

More recently, spinal implants have been developed that allow motionbetween the adjacent vertebrae, thereby restoring normal function to thevertebrae. While these implants have been met with great success, theytypically require an anterior surgical approach to be used to positionthe implant between adjacent vertebrae so as to avoid contact with thespinal cord. Most anterior surgical approaches, however, tend to be moreinvasive than posterior approaches due to the nature and amount of theanatomy that needs to be displaced in order to successfully access thedisc space.

Accordingly, there remains a need for improved methods and devices forreplacing a spinal disc, and in particular to methods and devices thatuse a posterior surgical approach.

BRIEF SUMMARY OF THE INVENTION

The present invention provides various spinal implants and methods forstabilizing the spine. In one exemplary embodiment, a spinal discprosthesis is provided having an anterior portion that is adapted to bepositioned between adjacent vertebrae, and a posterior portion that isadapted to extend around a spinal cord. In certain exemplaryembodiments, the implant can be substantially C-shaped.

While the implant can have a variety of configurations, in one exemplaryembodiment the anterior portion of the implant can be adapted to allowadjacent vertebrae to articulate relative to one another. For example,the anterior portion of the implant can include first and second domedsurfaces formed thereon. Alternatively, or in addition, the anteriorportion of the implant can be formed from a compressible material or caninclude a compressible member to allow movement between the adjacentvertebrae.

In another exemplary embodiment, the anterior portion of the implant caninclude opposed arms having a central member disposed therebetween. Thecentral member can have a variety of configurations. For example, it canbe formed from or can include a compressible material, or it can be inthe form of an inflatable member. The central member can be separatefrom the opposed arms, or it can be fixedly or movably coupled to theopposed arms using a variety of techniques. For example, in oneexemplary embodiment at least one of the opposed arms can include anopening formed therein for seating a portion of the central member. Thecentral member can include wings extending from opposed sides thereof,and the opposed arms of the anterior portion of the implant can includeopenings formed therein for receiving the wings.

Exemplary methods for replacing a spinal disc between adjacent vertebraeare also provided. In one exemplary embodiment, the method can includeremoving a spinal disc disposed between adjacent vertebrae, andpositioning a posterior portion of an implant around a spinal cord andpositioning an anterior portion of the implant between the adjacentvertebrae. The implant can be configured to allow movement of theadjacent vertebrae. In an exemplary embodiment, the implant ispositioned between the adjacent vertebrae using a posterior surgicalapproach.

In another exemplary embodiment, the method can include positioning acentral member between the adjacent vertebrae. In certain embodiments,the central member can be positioned between the adjacent vertebraeprior to positioning the implant, and the anterior portion of theimplant can be positioned around the central member. In otherembodiments, the method can include inflating a central memberpositioned between opposed arms of the anterior portion of the implant.

In yet another exemplary embodiment, a method for stabilizing adjacentvertebrae is provided and includes positioning a central member betweenadjacent vertebrae, positioning a posterior portion of an implant arounda spinal cord, and positioning opposed arms of an anterior portion ofthe implant on opposed lateral sides of the central member. In oneexemplary embodiment, the opposed arms of the anterior portion of theimplant can be positioned on opposed lateral sides of the central memberby sliding the opposed arms around the central member such that wingmembers extending from opposed lateral sides of the central member arereceived within openings formed in the opposed arms. In anotherexemplary embodiment, the central member can be implanted using aposterio-lateral approach, and the implant can be implanted using aposterior approach.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more fully understood from the following detaileddescription taken in conjunction with the accompanying drawings, inwhich:

FIG. 1A is a superior perspective view of one exemplary embodiment of aC-shaped implant;

FIG. 1B is a cross-sectional view of the C-shaped implant shown in FIG.1A taken across line B-B;

FIG. 1C is a superior perspective view of the C-shaped implant shown inFIG. 1A implanted between adjacent vertebrae, showing only the inferiorvertebra;

FIG. 1D is a posterior perspective view of the C-shaped implant shown inFIG. 1A implanted between adjacent vertebrae;

FIG. 2A is a superior perspective view of another exemplary embodimentof a C-shaped implant having a central member;

FIG. 2B is a cross-sectional view of an anterior portion of the C-shapedimplant shown in FIG. 2A taken across line B-B;

FIG. 2C is a superior perspective view of the C-shaped implant shown inFIG. 2A implanted between adjacent vertebrae, showing only the inferiorvertebra;

FIG. 3A is a perspective view of yet another exemplary embodiment of aC-shaped implant having a central member;

FIG. 3B is a cross-sectional view of an anterior portion of the C-shapedimplant shown in FIG. 3A taken across line B-B; and

FIG. 3C is a superior perspective view of the C-shaped implant shown inFIG. 3A implanted between adjacent vertebrae, showing only the inferiorvertebra.

DETAILED DESCRIPTION OF THE INVENTION

Certain exemplary embodiments will now be described to provide anoverall understanding of the principles of the structure, function,manufacture, and use of the devices and methods disclosed herein. One ormore examples of these embodiments are illustrated in the accompanyingdrawings. Those of ordinary skill in the art will understand that thedevices and methods specifically described herein and illustrated in theaccompanying drawings are non-limiting exemplary embodiments and thatthe scope of the present invention is defined solely by the claims. Thefeatures illustrated or described in connection with one exemplaryembodiment may be combined with the features of other embodiments. Suchmodifications and variations are intended to be included within thescope of the present invention.

The present invention provides various methods and devices for repairingor replacing damaged, injured, diseased, or otherwise unhealthyintervertebral discs. In one exemplary embodiment, an implant isprovided having a shape that allows the implant to be positioned betweenadjacent vertebrae using a posterior approach while avoiding contactwith the spinal cord. In certain exemplary embodiments, the implant canalso be configured to allow motion between the adjacent vertebrae.

FIGS. 1A and 1B illustrate one exemplary embodiment of a spinal implant10 having a substantially U-shaped or C-shaped unitary configuration. Inparticular, the implant 10 includes a posterior portion 12 a that isadapted to be positioned around a patient's spinal cord to allow for aposterior surgical approach, and an anterior portion 12 b that isadapted to be disposed between adjacent vertebrae. A person skilled inthe art will appreciate that the terms “U-shaped” or “C-shaped” areintended to include any implant 10 having a generally or partiallycurved structure with an opening in one side thereof. Further, theseterms are intended to include any implant that has an open anteriorportion and a posterior portion that can be disposed around a spinalcord, and an anterior portion that can be disposed between adjacentvertebrae. The shape and configuration of the implant 100 is notintended to be limited to only a U- or C-shaped configuration.

The posterior portion 12 a of the implant 10 can have a variety ofshapes and sizes, but in the illustrated exemplary embodiment theposterior portion 12 a is in the form of a U-shaped, C-shaped, orsemi-circular member having a relatively large central opening 18 aformed therein. Such a shape allows the posterior portion 12 a to bepositioned around the spinal cord in a patient's spinal column. Theposterior portion 12 a can also have a relatively low profile, so as toallow the posterior portion 12 a to be positioned between the spinousprocesses of adjacent vertebrae. A person skilled in the art willappreciate that the posterior portion 12 a can have a variety of othershapes, and that the shape can be adapted based on the intended use. Forexample, in the illustrated exemplary embodiment the facets of theadjacent vertebrae are preferably removed to allow the posterior portion12 a to be positioned around the spinal cord. However, the posteriorportion 12 a of the implant 10 could be shaped to allow the facets onthe adjacent vertebrae to remain intact and optionally to articulaterelative thereto.

The anterior portion 12 b of the implant 10 can also have a variety ofshapes and sizes, but in the illustrated exemplary embodiment theanterior portion 12 b of the implant 10 includes opposed arms 14, 16that extend from the posterior portion 12 a in a substantially parallelarrangement, and that define an opening 18 b therebetween. The opening18 b between the arms 14, 16 can be smaller than the opening 18 a at theposterior portion 12 a of the implant 10, but it is preferably largeenough to allow the spinal cord to pass therethrough when the implant 10is being implanted. While the shape and size of each arm 14, 16 canvary, in one exemplary embodiment each arm 14, 16 is in the form of alobe that extends from the posterior portion 12 a, and that has a heighth₁, h₂ that is greater than a height h₃ of the posterior portion 12 a,and a width w₁, w₂ that is greater than a width w₃ of the posteriorportion 12 a of the implant 10. Such a configuration allows the arms 14,16 to occupy additional space between the adjacent vertebrae, therebyproviding sufficient support for the vertebrae.

The opposed arms 14, 16 can also include a variety of other featuresthat can vary depending on the intended use and desired result onceimplanted. For example, in one exemplary embodiment each arm 14, 16 canhave a shape that is adapted to allow the adjacent vertebrae toarticulate relative thereto. For example, as shown in FIG. 1B, each arm14, 16 includes domed superior and inferior surfaces 14 s, 16 s, 14 i,16 i. The domed surfaces 14 s, 16 s, 14 i, 16 i can be formed on anyportion of each arm 14, 16, but in an exemplary embodiment the domedsurfaces 14 s, 16 s, 14 i, 16 i are formed along the anterior portion ofthe implant 10 adjacent to the terminal end of each arm 14, 16. As aresult, when the arms 14, 16 are positioned between adjacent vertebrae,the domed surfaces 14 s, 16 s, 14 i, 16 i will be substantiallycentrally located relative to the adjacent vertebrae, thereby allowingthe vertebrae to articulate relative thereto. While domed surfaces 14 s,16 s, 14 i, 16 i are shown, the arms 14, 16 can have a variety of otherconfigurations to allow articulation of adjacent vertebrae. For example,each arm 14, 16 can include a ball or other member movably disposedtherein.

In another exemplary embodiment, each arm 14, 16 can be configured toabsorb shock between the adjacent vertebrae. For example, the arms 14,16, or a portion of the arms 14, 16, can be compressible. This can beachieved by forming the arms 14, 16 from a compressible material,embedding a compressible material in the arms 14, 16, or by coupling acompressible material to a portion of the arms 14, 16. The arms 14, 16can thus be formed from a single unitary component, or they can beformed from separate components that are coupled to one another and tothe posterior portion 12 a. Suitable compressible materials include, byway of non-limiting example, biocompatible polymers and metals.

The implant 10 can also include features to facilitate engagement of theadjacent vertebrae. In an exemplary embodiment, where engagementfeatures are included, at least a portion of the implant 10 ispreferably compressible to allow movement between the adjacentvertebrae. Techniques for mating the implant 10 to adjacent vertebraeinclude, by way of non-limiting example, surface features, such asteeth, that engage the endplates of the vertebrae, surface coatings ormaterials that allow bone growth into the implant 10 to occur, or othermaterials or features that will engage the adjacent vertebrae.

FIGS. 1C and 1D illustrate the implant 10 in use implant betweenadjacent vertebrae V_(s), V_(i) (FIG. 1C only illustrates the inferiorvertebra V_(i)). In an exemplary embodiment, the spinal column isaccessed using a posterior surgical approach (which can includeposterio-lateral approaches). Once the spinal column is accessed, andprior to positioning the implant 10 between adjacent superior andinferior vertebrae V_(s), V_(i), standard surgical techniques can beused to remove the natural disc disposed between the adjacent vertebraeV_(s), V_(i), and preferably to remove the facet joints between theadjacent vertebrae V_(s), V_(i). While not shown or described, facetreplacement implants can be used in combination with implant 10 torestore function or otherwise replace the removed facet joints.

Once the disc and facets are removed and the adjacent vertebrae areprepared, the implant 10 can be guided between the adjacent vertebraeV_(s), V_(i) by passing the spinal cord between the opposed arms 14, 16and into the central opening 18 a. A spinal distractor or other devicesknown in the art can be used to distract the adjacent vertebrae V_(s),V_(i) and guide the implant 10 therebetween. Alternatively, the implant10 can have a shape that is adapted to distract the vertebrae V_(s),V_(i) as the implant 10 is inserted therebetween. Once implanted, asshown, the opposed arms 14, 16 are positioned between the adjacentvertebrae V_(s), V_(i), and the posterior portion 12 a of the implant ispositioned around the spinal cord and between the spinous processesS_(s), S_(i) of the adjacent vertebrae V_(s), V_(i). The adjacentvertebrae V_(s), V_(i) can articulate relative to the implant 10.

In another exemplary embodiment, the spinal implant can include a coreor central member disposed between the opposed arms of the implant.FIGS. 2A-2C illustrate one exemplary embodiment of an implant 100 havinga posterior portion 112 a, an anterior portion 112 b with opposed arms114, 116, and a central member 120 disposed between the opposed arms114, 116. While the central member 120 can have a variety of shapes andsizes, in the illustrated embodiment the central member 120 has asubstantially rectangular portion 120 a that extends between the opposedarms 114, 116, and opposed wing-members 122 a, 122 b extending fromopposed sides of the rectangular portion 120 a. The wing members 122 a,122 b can extend into opposed openings 114 o, 116 o formed on theinwardly facing surfaces of the opposed arms 114, 116, as shown in FIG.2B, to couple the central member 120 to the arms 114, 116. The openings114 o, 116 o can be sized to provide a compression or interference fitwith the wing members 122 a, 122 b, thereby providing a substantiallyrigid connection between the central member 120 and the arms 114, 116.The central member 120 can, however, be formed form a flexible materialto allow movement between the central member 120 and the arms 114, 116,if desired. Alternatively, the openings 114 o, 116 o can each have asize that is greater than a size of the wing members 122 a, 122 b toallow some movement between the central member 120 and the arms 114,116. A movable configuration is particularly advantageous as it allowseach arm 114, 116 to move with relative movement of the adjacentvertebrae. The central member 120 can also be adapted to move relativeto the adjacent vertebrae. For example, the central member 120 caninclude domed or curved superior and inferior surfaces to allow theadjacent vertebrae to articulate relative thereto. Alternatively, thecentral member 120 can be adapted to fixedly couple to the adjacentvertebrae. As previously described, techniques such as surface features,bone growth materials, etc., can be used to provide a rigid connectionwith the vertebrae.

FIGS. 3A-3C illustrate another exemplary embodiment of an implant 200having a central member 220 disposed between opposed arms 214, 216 ofthe anterior portion 212 b of the implant 200. The central member 220 issimilar to the central member 120 shown in FIGS. 2A-2C, and includes arectangular portion 220 a with wing members 222 a, 222 b extending fromopposed sides thereof. In this embodiment, the wing members 222 a, 222 bare adapted to be disposed within openings 214 o, 216 o that extendentirely through each arm 214, 216. As a result, each arm 214, 216 isseparated into a superior portion 214 s, 216 s and an inferior portion214 i, 216 i. Such a configuration can allow the superior and inferiorportions 214 s, 216 s, 214 i, 216 i of each arm 214, 216 to moverelative to one another. For example, the central member 220, or atleast some or all of the wing members 222 a, 222 b, can be formed from acompressible material. Thus, when the adjacent vertebrae move relativeto one another, the superior and inferior portions 214 s, 216 s, 214 i,216 i of the arms 214, 216 can move to compress the wing members 222 a,222 b therebetween. The compressible wing members 222 a, 222 b are alsoparticularly advantageous as they can be effective to absorb shock.

A person skilled in the art will appreciate that the implant can includea central member having a variety of other shapes, sizes, andconfigurations, and the particular configuration of the central membercan vary depending on the intended use. By way of non-limiting example,the central member can be in the form of a ball, a disc, or other memberthat has a shape that allows the adjacent vertebrae to articulaterelative thereto. The central member can also include multiple pieces.For example, the central member can include a superior endplate memberand an inferior endplate member with a movable core disposedtherebetween.

The central member can also be formed from a variety of materials. Forexample, in one exemplary embodiment the central member can be formedfrom a rigid material, such as a biocompatible plastic or metal.Alternatively, the central member, or a portion of the central member,can be formed from or include a flexible and/or compressible material toallow the central member to flex and/or to be compressed between theadjacent vertebrae. In another exemplary embodiment, the central membercan be inflatable such that it can be implanted in a deflated state, andthen inflated to restore height and/or occupy the disc space between theadjacent vertebrae. Where an inflatable central member is used, thecentral member can be separate from the C-shaped implant, or it can becoupled to one or both arms of the implant. In use, the inflatablecentral member can be inflated prior to positioning the implant betweenadjacent vertebrae, or after the implant is positioned between theadjacent vertebrae. A person skilled in the art will appreciate that thecentral member can have a variety of other configurations.

In use, a variety of surgical techniques can be used to position animplant having a core or central member between adjacent vertebrae, andthe particular procedure can vary depending on the configuration of thecentral member. Referring to FIG. 2C, in one embodiment the centralmember 120 can be inflatable. With the central member 120 in a deflatedstate, the implant 100 can be positioned between adjacent vertebraeusing a posterior approach as previously described with respect to FIGS.1C and 1D. Once properly positioned between the adjacent vertebrae, aninflation medium, such as air or fluid, e.g., saline, can be introducedinto the central member 120 to inflate the central member 120. As aresult, the central member 120 will extend between the opposed arms 114,116 to couple to the arms 114, 116. The inflation medium can optionallybe adapted to harden to form a rigid central member 120.

Alternatively, continuing to refer to FIG. 2C, the central member 120can be pre-disposed between the adjacent vertebrae and the C-shapedportion of the implant 100 can be introduced around the central member120. Where such a technique is used, the opposed arms 114, 116 arepreferably flexible to allow the arms 114, 116 to flex around the wingmembers 122 a, 122 b of the central member 120 until the wing members122 a, 112 b are positioned within the openings 114 o, 116 o in the arms114, 116.

In another exemplary embodiment, referring to FIG. 3C, the centralmember 220 of the implant 200 can be positioned between the adjacentvertebrae using an anterior or posterio-lateral surgical approach. TheC-shaped portion of the implant 100 can then be guided between thevertebrae, using a posterior approach, by passing the spinal cordbetween the opposed arms 114, 116, and then sliding the opposed arms114, 116 around the central member 220. Alternatively, as discussedabove, the central member 220 can be inflatable, and it can bepre-positioned between the adjacent vertebrae or inflated after theimplant 220 is implanted. A person skilled in the art will appreciatethat a variety of other techniques can be used to position the implantsdisclosed herein between adjacent vertebrae.

One skilled in the art will appreciate further features and advantagesof the invention based on the above-described embodiments. Accordingly,the invention is not to be limited by what has been particularly shownand described, except as indicated by the appended claims. Allpublications and references cited herein are expressly incorporatedherein by reference in their entirety.

1. A spinal disc prosthesis, comprising: a substantially c-shaped memberhaving an anterior portion adapted to be positioned between adjacentvertebrae and adapted to allow adjacent vertebrae to articulate relativeto one another, and a posterior portion adapted to extend around aspinal cord, the anterior portion having a height that is greater than aheight of the posterior portion.
 2. The implant of claim 1, wherein theanterior portion of the c-shaped member includes first and second domedsurfaces formed thereon.
 3. The implant of claim 1, wherein the c-shapedmember has a unitary construction.
 4. The implant of claim 1, whereinthe anterior portion of the c-shaped member includes opposed arms havinga central member disposed therebetween.
 5. The implant of claim 4,wherein the central member is inflatable.
 6. The implant of claim 4,wherein the central member is movably disposed between the opposed arms.7. The implant of claim 4, wherein the central member is formed from acompressible material.
 8. The implant of claim 4, wherein the centralmember includes wings extending from opposed sides thereof, and whereinthe opposed arms of the anterior portion of the c-shaped member includeopenings formed therein for receiving the wings.
 9. A spinal discprosthesis, comprising: a substantially c-shaped member having ananterior portion adapted to be positioned between adjacent vertebrae andadapted to allow adjacent vertebrae to articulate relative to oneanother, and a posterior portion adapted to extend around a spinal cord,the anterior portion including opposed arms having a central memberdisposed therebetween, at least one of the opposed arms including anopening formed therein for seating a portion of the central member. 10.A method for replacing a spinal disc between adjacent vertebrae,comprising: removing a spinal disc disposed between adjacent vertebrae;and positioning a posterior portion of an implant around a spinal cordand positioning an anterior portion of the implant between the adjacentvertebrae, the implant being configured to allow movement of theadjacent vertebrae.
 11. The method of claim 10, wherein the implant ispositioned between the adjacent vertebrae using a posterior surgicalapproach.
 12. The method of claim 10, wherein the anterior portion ofthe implant includes at least one domed surface formed thereon andadapted to allow articulation of the adjacent vertebrae relativethereto.
 13. The method of claim 10, further comprising positioning acentral member between the adjacent vertebrae.
 14. The method of claim13, wherein the central member is positioned between the adjacentvertebrae prior to positioning the implant, and wherein the anteriorportion of the implant is positioned around the central member.
 15. Themethod of claim 10, further comprising inflating a central memberpositioned between opposed arms of the anterior portion of the implant.16. The method of claim 10, wherein the implant is substantiallyc-shaped such that the anterior portion of the implant includes opposedarms that are positioned between the adjacent vertebrae.
 17. The methodof claim 10, further comprising, prior to positioning the implant,removing the natural disc from between the adjacent vertebrae.
 18. Amethod for stabilizing adjacent vertebrae, comprising: positioning acentral member between adjacent vertebrae; positioning a posteriorportion of an implant around a spinal cord, and positioning opposed armsof an anterior portion of the implant on opposed lateral sides of thecentral member.
 19. The method of claim 18, wherein positioning opposedarms of an anterior portion of the implant on opposed lateral sides ofthe central member comprises sliding the opposed arms around the centralmember such that wing members extending from opposed lateral sides ofthe central member are received within openings formed in the opposedarms.
 20. The method of claim 18, wherein the central member isimplanted using an posterio-lateral approach, and the implant isimplanted using a posterior approach.